Unions want the Fair Work Commission to be given new powers to award compensation for underpayment of wages, saying Australia needs a “tough cop” to battle wage theft.

The Australian Council of Trade Unions secretary, Sally McManus, will outline the latest tranche of union demands, including more power to lift minimum wages and award conditions, in a speech to the Per Capita thinktank on Friday.

In a preview of the speech, seen by Guardian Australia, McManus cites the cases of underpayment at franchises of 7-Eleven, Dominos and Caltex to argue that it is “difficult to enforce rights” and workers are “not even [being] paid the minimum wage” as a result.

She argues that working people cannot afford to take their employers to court and fight cases that take up to 18 months. Even then, workers face victimisation if they do.

Tenancy and consumer complaints are dealt with by tribunals, she says, so the industrial commission should similarly be able to provide “quick, simple, [and] accessible justice” for workers.

The Fair Work Ombudsman is “under-resourced and conflicted”, McManus says, because it has 200 inspectors to check payments to a workforce of 12 million workers and has other roles including prosecuting breaches of industrial law by unions. “We need a tough cop back to deal with wage theft,” she says.

“If there is a dispute over pay at one 7-Eleven store then the commission should be empowered to summons not just the store owner but the franchisor.

“If there is a dispute over entitlements on a building site then, where appropriate, the commission should be able to make orders against not just the subcontractor but also the head builder.”

McManus argues that the FWC can review awards but the law requires new terms to be “necessary” to meet a list of objectives set by parliament rather than the simpler test of whether a claim is “fair and reasonable”.

When the industrial umpire had arbitration powers to grant claims on merit, unions were able to win the eight-hour day, paid annual leave, paid sick leave, superannuation and retrenchment pay, she says.

The ACTU secretary also wants to lower the bar for awarding minimum wage rises.